So, there have been a lot of questions as to what exactly is Rammed Earth. Well, I'll tell you. It's pretty amazing stuff, all it is is a mixture of different types of soil that is compacted/rammed into a form. Think of making a really nice sand castle. The key to making it work is having the correct mixture of sand, gravel, and most importantly, CLAY. Ideally you want between 20-40% clay in your soil. The clay binds the sand and other aggregate together. Cement may also be added as a stabilizer if there isn't enough clay in the mixture. For our rammed earth (RE) walls we have about a 30% clay soil content. It took forever to find the right color and clay content. So, our mixture for the wall is a 45% sand and 30% clay mixture with about 12.5% cement and 12.5% road base gravel. You mix this all together and add just enough water to make the mixture ball together in your hand. It is a very dry mixture. This is poured into the forms about 8 inches at a time and then is rammed down with a pneumatic or hand tamper. That is what creates the layers in the wall. The gray layers were done with a different soil clay mixture that had a little less clay, which we compensated for with more cement. I hope that clears up what RE is.
T1T2